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How to: Maintain your batteries

John Baxter |October 01, 2010

Test and clean routinely

For power needed to run cab accessories, most trucks today need deep-cycle batteries with a lot of reserve capacity rated at a low amperage draw. A battery with, say, 200 hours reserve capacity has fewer, thicker plates than traditional batteries designed mainly for cranking the engine. It will last much longer with overnight shutdowns. Testing of batteries and cleanup of their connections every six months, or sooner if corrosion is noticed, will prevent no-starts while also minimizing electrical system repair costs.

2. If doing this for the first time, draw a diagram of the cable connections before proceeding. Then, remove all the negative terminal attaching nuts and disconnect negative cables to prevent a short circuit.

3. Loosen all the battery hold-down nuts and remove the hold-down bracket for access.

4. Remove the cell covers. Test each cell by drawing the electrolyte fluid into a hydrometer. In a healthy cell, all the balls float near the top.

5. Balls floating near the bottom of the hydrometer indicate a bad cell. In this case, you should measure voltage with the engine off. A battery is dead at 12.1 volts, and fully charged at 12.6 volts. Even if only one battery in a group is bad, it’s best to replace them all to make sure they all do the same amount of work.

6. If any of the hold-down bolts or other parts break during disassembly or show signs of severe corrosion, replace them. Secure mounting means less vibration and longer battery life.

7. Clean all cable connections with a male drill-mounted wire brush.

8. Clean all the battery posts with the corresponding female brush – even on a new battery, to ensure good connections.

9. After replacing all the caps and the mounting bracket, tighten the bracket mounting nuts securely. Then install and gently tighten each positive cable and post connector.